Heated catalysts are used in motor vehicles to improve emission control by reducing hydrocarbon (HC) and carbon monoxide (CO) emissions. Such catalysts only work at fairly high temperatures. For example, when an engine is first started, the catalyst may not be effective in removing emissions in the exhaust until the catalyst reaches an operating temperature commonly referred to as its light-off temperature, or the point where conversion of CO or HC has reached 50% efficiency. Starting an engine with such a catalyst that needs to be warmed up to the light-off temperature, or cold-starting, may comprise a repetitive act particularly seen in hybrid vehicles that repeatedly start, stop, and restart the engine during normal operation.
Accordingly, one solution to engine cold-starting is to preheat the catalyst, to reduce an amount of time for the catalyst to reach its operating temperature. Such solutions may employ electric heating elements, whereby electrical energy supplied to the heating element raises the temperature of the catalyst quickly, thus improving its effectiveness as soon as possible after the engine starts.
Where such a heating element is included in hybrid vehicles, it is necessary to diagnose the heating element to ensure it is functioning as desired or expected. Such diagnostics may reduce or avoid undesired emissions being emitted to atmosphere. One example of such a diagnostic includes imbedding thermocouples within the catalyst, and monitoring for temperature gain when the heating element is activated. However, such a solution incurs additional cost, complexity, and additional diagnostics for the thermocouple itself. Accordingly, other diagnostics that utilize existing hardware present in engine systems are desired.
The inventors herein have recognized the above-mentioned issues, and have herein developed systems and methods to at least partially address them. In one example, a method comprises diagnosing an electric heater configured to increase a temperature of an exhaust catalyst positioned in an exhaust system of an engine of a vehicle by activating the electric heater, routing air flow from the exhaust system to an intake of the engine, and indicating the electric heater is degraded based on a test temperature in the intake being below a threshold temperature. In this way, the electric heater may be diagnosed without embedding thermocouples within the catalyst.
In one example, the method further comprises routing air flow from the exhaust system to the intake of the engine without activating the electric heater prior to activating the electric heater, to obtain a baseline temperature in the intake of the engine, and where the threshold temperature is a predetermined amount greater than the baseline temperature. In such an example, obtaining the baseline temperature and the test temperature is via an intake air temperature sensor.
In another example of the method, the method further comprises under conditions where the engine includes an electric booster positioned in the intake of the engine, routing air flow from the exhaust system to the intake via activating the electric booster in a reverse orientation to apply negative pressure with respect to atmospheric pressure on the exhaust system. Alternatively, under conditions where the engine does not include the electric booster, or where the electric booster is indicated to be degraded, the method may include routing air flow from the exhaust system to the intake via rotating the engine unfueled in reverse to apply negative pressure with respect to atmospheric pressure on the exhaust system. In either example, the method may include commanding fully open a throttle positioned in the intake in order to route air flow from the exhaust system to the intake of the engine.
In an example where routing air flow from the exhaust system to the intake via activating the electric booster in reverse, the method may further comprise commanding open an exhaust gas recirculation valve positioned in an exhaust gas recirculation passage, commanding open a wastegate valve positioned in a wastegate passage, the wastegate passage configured to bypass a turbine positioned in the exhaust system, and commanding closed an electric booster bypass valve configured in parallel with the electric booster and further configured to enable air flow to bypass the electric booster when the electric bypass valve is commanded open. In such an example, the method may further comprise sealing all cylinders of the engine via commanding closed intake and exhaust valves coupled to all cylinders of the engine.
In one example of the method, the vehicle may comprise a vehicle operated via a vehicle operator, or may comprise an autonomous vehicle. In either case, diagnosing the electric heater may include conditions where the vehicle is unoccupied, or in other words indicated to be unoccupied.
Furthermore, in an example of the method, the engine may be equipped with a start/stop feature that automatically stops the engine in response to a set of predetermined conditions being met while the engine is combusting air and fuel. In such an example, under conditions where the electric heater is indicated to be degraded, the method may include updating the start/stop feature to prevent the engine from stopping at start/stop events where it is predicted that the temperature of the exhaust catalyst will drop below a threshold exhaust catalyst temperature during the start/stop event. In this way, undesired emissions released to the environment may be effectively reduced.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.